Hi Heiko
Your query looks fine. However, are you using deltasync.maxDateFromLastRun in the OData adapter or in the SFAPI adapter? I believe it is meant to be used only in the SFAPI adpater (for Compound Employee etc.). User is an OData entity.
Have you raised an incident with SuccessFactors? They are very prompt with their support.
I am looping in Finny Babu and Bikash Prakash Mishra who are SFSF Gurus for clarification.
Regards
Arijit